Asymmetry study in Siganus rivulatus Forsskal, 1775 (Family: Siganidae) collected from the Arabian Sea coasts of Oman.

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1 Qud. Mus. St. Nt. Livorno, 24: 1-5 ( ) 1 Asymmetry study in Signus rivultus Forsskl, 1775 (Fmily: Signide) collected from the Arbin Se costs of Omn. Jum Al-Mmry 1, Lith Jwd 1*, Hithem Al-Busidi 1, Ahmed Al-Alwi 2, Smi Al-Ghrbi 2, Luqmn Al-Hsni 2, Sultn Al-Mrzouqi 2, Iss Al-Ruwhi 2, Jml Al-Yrubi 2, Abdulrhim Al-Zhli 2, Mohmed Al-Mrzouqi 1, Soud Al-Nbsi 3 SUMMARY: Asymmetry nlyses hve been crried out for some bilterl chrcters of Signus rivultus Forsskl, 1775 collected from the Arbin Se costs of Omn. The results showed tht the level of symmetry of the chrcters pectorl fin ry count nd postorbitl length ws the highest mong those symmetry vlues obtined for the remining chrcters studied. The lowest vlue ws tht for hed length. An incresing trend in the symmetry vlue with fish length is lso obtined for preorbitl length, hed length nd pectorl fin ry count. The possible cuse of the symmetry in this species is herein discussed in reltion to different pollutnts nd their presence in the re. Keywords: symmetry, Signus, Arbin Se, Omn RIASSUNTO: Sono stte svolte nlisi sull simmetri di lcuni crtteri bilterli di Signus rivultus Forsskl, 1775 provenienti dlle coste dell Omn sul Mre Arbico. I risultti mostrno che il livello di simmetri del numero dei rggi delle pinne pettorli e quello dell lunghezz dell osso postorbitle sono i più elevti tr crtteri studiti. Il vlore più bsso è stto quello reltivo ll lunghezz dell test. I livelli di simmetri dell lunghezz dell osso preorbitle, dell lunghezz dell test e del numero dei rggi dell pinn pettorle hnno mostrto l tendenz d umentre con le dimensioni del pesce. L possibile cus delle simmetrie in quest specie è stt nche mess in relzione con differenti sostnze inquinnti e con l loro presenz nell re. Prole chive: simmetri, Signus, Mre Arbico, Omn Introduction Members of the fmily Signide re mong the importnt demersl fishes in the Arbin Se costs of Omn. Severl species hve been observed in the re nd long the costs of Omn (Rndll, 1995). The effect of the environmentl fctors on meristic nd morphometric chrcters show significnt defect once those chrcters becme exposed to (Fowler, 1970). Environmentl stress is the totl environmentl influences tht ffect the structure nd function of n orgnism in such wy tht their Neo-Drwinin fitness is reduced (Clow, 1989). Asymmetry is the differentil development of bilterl chrcter between the sides of n orgnism (Vn Vllen, 1962; Plmer, Strobeck 1986; Lery, Allendorf, 1989). On the other hnd, fluctuting symmetry results from the inbility of individuls to undergo identicl development of trit on both sides of the body. It is lso suggested tht fluctuting symmetry represents mesure of the sensitivity of development 1. Mrine Science nd Fisheries Centre, Ministry of Fisheries Welth, Sultnte of Omn, P.O. Box 427, Postl Code 100 Musct. 2. Deprtment of Mrine Science nd Fisheries, Sultn Qboos University, P. O. Box 34, Al-khud 123, Sultnte of Omn. * Corresponding uthor: lith_jwd@hotmil.com

2 2 Jum Al-Mmry et l. to environmentl stress (Moller, Pominkows, 1993). Asymmetry usully incresed under environmentl stresses, due to the filure of homeosttic regultory mechnism. Such developmentl effects might occur before the concentrtion of toxicnt in wter or food reches level high enough to produce morbidity (Bengtsson, Hindberg, 1985). This work studied the bilterl symmetry phenomenon in selected morphologicl chrcters of the signid species, Signus rivultus collected from the Arbin Se costs of Omn. Mteril nd methods Specimens of S. rivultus were collected from the Arbin Se cost of Omn on the 3 rd Jnury This signid species is dmersl nd it is found on snd nd muddy bottoms nd it is common on the Omni costs of the Arbin Se. The five bilterl chrcters used to compre symmetry were s follows: (1) Length of the pre-orbitl distnce (mm): mesured from mouth to the nterior edge of the orbit. (2) Length of the post-orbitl distnce (mm): mesured from the posterior edge of the eye to the posterior edge of the operculum. (3) Eye dimeter (mm): mesured from the nterior to the posterior edges of the eye. (4) Hed length (mm): mesured from mouth to the posterior edge of operculum. Meristic chrcters: (5) Number of pectorl fin rys: count of the totl number of pectorl fin ry, including the most upper ry. Most chrcters were counted nd mesured under binoculr dissecting microscope. For specimens too lrge to fit under microscope, mgnifying glss ws used. In the sttisticl nlysis, the squre coefficient of symmetry vrition (CV 2 ) for meristic nd morphometric chrcter ws clculted ccording to Vlentine et l. (1973) s: CV 2 = (S X 100/X ) Where S is the stndrd devition of the signed difference, nd X is the men of the chrcter, which is clculted by dding the bsolute scores for both sides nd dividing by the smple size. To eliminte scling problems ssocited with growth in morphometric chrcters (non discrete, Chrcter CV 2 N mesurble), ech mesurements ws divided by conventionl stndrdizing mesurement (e.g. hed length ws used in the present study). Every morphometric mesurement ws treted in similr squred coefficient of symmetry ws determined s before. Results The results of symmetry dt nlysis of the previously listed chrcters of S. rivultus collected Arbin Se costs of Omn re shown in Tble 1. The highest vlue ws recorded for pectorl fin ry count nd postorbitl length. The percentge of the individuls showing symmetry in the postorbitl chrcter ws the highest mong the percentges recorded for the five chrcters (64.83% of the totl fish studied) nd the lowest percentge ws for the individuls with symmetry in the chrcter hed length (44.89 % of the totl fish studied). Individuls of S. rivultus were grouped into length clsses (Tb. 2). An incresing trend in the symmetry vlue with fish length is lso obtined for preorbitl length, hed length nd number of pectorl fin ry. Discussion Chrcter men Preorbitl length Postorbitl length Eye dimeter N. Pectorl Fin ry Hed length % of individuls with symmetry Tb. 1. Squred coefficient symmetry (CV 2 ) vlues nd chrcter mens (X ) of Signus rivultus. Tb. 1. Qudrto del coefficiente di simmetri (CV 2 ) vlori e crtteri medi di Signus rivultus. There is some vrition in the symmetry vlues mong the five morphologicl chrcters studied in S. rivultus. At the present time it is impossible to evlute the level of symmetry of those chrcters nd to determine if they re higher or lower thn verge due to the lck of dt regrding nturl symmetry in this prt of the world. However, chrcters like pectorl fin ry count nd postorbitl length showed hi-

3 Asymmetry study in Signus rivultus 3 Size Clss n CV 2 chrcter men X r + l % of individuls with symmetry Preorbitl length Totl 94 Postorbitl length Totl 94 Eye lens dimeter Totl 94 Hed length Totl 94 Number of pectorl fin ry Totl 94 Tb. 2. Squred coefficient of symmetry nd chrcter mens (X ) by size clss of Signus rivultus. Tb. 2. Qudrto del coefficiente di simmetri e medi dei crtteri (X r+1 ) per clssi di dimensioni di Signus rivultus. gher symmetry vlues thn those of the other chrcters studied. High symmetry vlues for pectorl fin ry count nd postorbitl length hve lso been recorded in severl freshwter nd mrine fish species (Al-Hssn et l., 1990; Al-Hssn, Hssn, 1994; Jwd, 2001; 2003; Jwd et l., 2010). Such greements in results of symmetry might indicte the vulnerbility of those two chrcters to immedite chnges in the environment. It is impossible t this stge to confirm tht these levels of symmetry correlte to vrious types of environmentl pollution, nd the morphology of the fish species in question is

4 4 Jum Al-Mmry et l. not vilble. However, bsed on previous studies, it is possible to conclude tht there is direct correltion between environmentl stress, due to pollution, nd symmetry in this species. Such environmentl fctors re present in the wters of the Arbin Se costs of Omn. On the other hnd, the low symmetry vlues displyed by the three other chrcters, preorbitl length, hed length nd eye dimeter, might be explined on the bsis tht those chrcters re less vulnerble to environmentl stresses. This my be the cse when the developmentl period of those chrcters does not coincide with the presence of dverse environmentl events (Jwd, 2003; Jwd et l., 2010). Other fctors, including genetic ones, might be responsible for the symmetry in these chrcters, but these cn not be discussed t this stge due to the lck of genetic dt on the ichthyofun of Omn. The origin nd cuse of symmetry in fish cn depend on severl fctors, one of which is environmentl stress, which leds to n incresed level of symmetry, but might occur t low levels before cusing wide spred deth (Bengtsson, Hindberg, 1985). Pollution of se wter nd sediments by hydrocrbons, hevy metls, pesticides nd orgnic mtter re considered the min cuse of environmentl stress. Pollution is not unusul for the Omni wters, s reports of dverse conditions in this prt of the world continue lerting people to locl ecologicl dissters (Rmmurthy, 1991; Bdwy, Al-Hrthy, 1991, Sen Gupt et l., 1993). The environmentl cuses might be nturl events. Severl fctors re known to produce nutritionl deficiencies such s vrious pthogens nd vrious popultion phenomen (Bengtsson, Hindberg, 1985), nd it is highly possible tht these fctors my be in ction in Omn Se, since they seem to be common in the qutic environment. Severl uthors hve shown reltionship between the coefficient of symmetry nd fish length (Al-Hssn et l., 1990; Al-Hssn, Hssn, 1994; Al-Hssn, Shwfi, 1997; Jwd et l., 2001; Jwd et l., 2010) where there ws trend of increse in the symmetry vlue with the increse in fish length. The results show trend of incresing symmetry with fish length for the preorbitl legth, hed length nd number of pectorl fin ry count. This trend is probbly the result of incomplete development; chrcter mens re lwys lowest in smller size clsses (Vlentine et l., 1973). The sme results were obtined by Vlentine et l. (1973) in selected fish species collected from Cliforni, U.S.A. They suggested two possible hypotheses tht my ccount for such trend; these re the ontogenetic chnges which re n increse in symmetry with size (ge) nd the possible historicl process which is seculr increse in symmetry. Acknowledgements We would like to thnk the Ministry of Fisheries Welth, the Agriculture nd Fisheries Development Fund nd the Mrine Science nd Fisheries Centre for giving us the opportunity to work on the fish smples within the qulittive nd quntittive distribution of mrine orgnisms in the Sultnte of Omn nd to provide the pproprite finncil support. References Al-Hssn L. A.J., Hssn S.S., Asymmetry study in Mystus pelusius collected from Shtt l-arb River, Bsrh, Irq. Pkistn Journl of Zoology, 26: Al-Hssn L. A. J., Shwfi N.A.A., Asymmetry nlysis in two mrine teleost fishes collected from the Red Se cost of Yemen. Pkistn Journl of Zoology, 29: Al-Hssn L. A. J., Al-Dubikel A.Y., Whb N. K., Al-Dhm N.K., Asymmetry nlysis in the ctfish, Heteropneustes fossilis collected from Shtt l-arb River, Bsrh, Irq. Rivist di Idrobiologi, 29: Bdwy M. I., Al-Hrthy F., Hydrocrbons in sewter, sediment nd oyster from the Omni costl wters. Bulletin of Environmentl Contmintion, 47: Bengtsson B. E., Hindberg M., Fish deformities nd pollution in some Swedish wters. Ambio, 14: Clow P., Proximte nd ultimte responses to stress in biologicl systems. Biologicl Journl of Linnen Society, 37: Fowler J. A.,1970. Control of vertebrl number in teleosts-n embryologicl problem. Qurterly Review of Biology, 45:

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